Solid state starters/controllers have found widespread use for controlling application of power to an AC induction motor. The conventional starter/controller, referred to hereinafter as simply a controller, uses solid state switches for controlling application of AC line voltage to the motor. The switches may be thyristors, such as silicon controlled rectifiers (SCRs) or triacs. The controller typically includes heat sinks associated with the SCR's for dissipating heat. A housing surrounds the SCRs. The housing may support a set of bus bars which carry current into and out of the controller. Controllers come in many different configurations that have different sizes of SCRs and bus bars to accommodate different current requirements. The size differences relate to current capacity and also physical size and usually require different housing parts to fit with each size.
Control of the SCRs is provided by a control circuit provided on a circuit board. The control circuit may include logic circuitry for commanding operation of the solid state switches and interface circuitry connected between the logic circuitry and the solid state switches. The logic circuitry may be identical for all of the different configurations. Instead, software may vary from configuration to configuration. Conversely, the interface circuitry may be unique to the voltage and current requirements of the SCRs being driven. Consequently, different circuit boards are required for each different configuration owing to the differences in interface circuitry. As a result, a manufacturer typically designs multiple different circuit boards resulting in higher costs and higher inventory requirements.
Additionally, the controller, in use, is generally mounted to a control panel. To do so, a sheet metal base plate is mounted to the heat sink. The sheet metal base plate is in turn mountable to the control panel. Further, the control circuit frequently includes user actuable switches for configuring operation of the controller. The switches are actuated by actuators moveably mounted to the housing. All of these different design configurations require use of multiple parts, again adding to inventory and thus manufacturing costs.
The present invention is directed to improvements in motor controller design.